This invention relates to a magnetic tape that can be used to test and adjust the alignment of a magnetic head having n gaps for recordings with n-channels or tracks, where n may be 1, 2 . . . , and to a process for determining and correcting the oblique angle (skew) of the gap(s) and, therefore, of the magnetic head having the gap(s). The magnetic tape contains parallel recordings of constant wave length and amplitude but differing phase angle.
For scanning small wave lengths in magnetic recording processes, the recording and reproduction gaps of the magnetic heads must be placed parallel to one another as accurately as possible and in general perpendicular to the direction of travel of the tape. Inaccurate adjustment of the gap results in a loss of level in a monochannel recording and reproduction. In multi-track recordings and reproductions, there is the added problem of a wave-dependent phase difference (see FIG. 1), which may result, for example, in the reproduction level varying with the frequency if reproduction channels are combined to form a single channel (stereo-mono compatability).
Various methods are known for adjusting the gaps of magnetic heads:
An adjustment tape on which short wave lengths are recorded is scanned by the magnetic head which is to be adjusted and the gap position of the head is varied until maximum level is obtained. This generally requires the gap to be turned several times through its optimum position and a correctly adjusted magnetic head must be displaced from its adjustment and readjusted.
DE-PS 1 522 975 discloses a magnetic tape which carries two phase-shifted recordings in two parallel tracks of equal width which are separated from one-another. The two tracks carry recordings of constant and small wave lengths whose phase positions race ahead of one another and lag behind one another by the same amount in separate sections. This test tape provides a simple and accurate method of adjusting the gap position for mono records but not multi-track recordings it requires at least two reproduction channels to be connected together or other maneuvers, such as mechanical adjustment of the magnetic gap by trial and error, to be carried out on the apparatus. Other test tapes are also disclosed in DE-AS 2 314 126 and in DD-PS 107 537. The teaching of these specifications also fails to impart a simple method of adjusting the gap of the head for n-channel recordings.
The problem therefore arose of finding a magnetic tape for testing and adjusting the position of the gap, which could carry out this test by means of the voltage level meters present for each channel without interfering with the apparatus itself or its wiring.